Vessel-sealing device including force-balance interface and electrosurgical system including same

ABSTRACT

A surgical instrument includes a housing having a shaft affixed thereto, a reciprocatable drive rod slideably disposed at least partially within the shaft, and a force applicator coupled to the drive rod. The shaft includes first and second jaw members attached to a distal end thereof, at least one of which movable relative to the other from a first position wherein the jaw members are disposed in spaced relation relative to one another to at least a second position closer to one another wherein the jaw members cooperate to grasp tissue therebetween. The force applicator and the drive rod mechanically communicate to impart movement to at least one of the jaw members. The bipolar forceps includes a handle assembly and a force-balance interface. The force-balance interface configured to translate a multiple of the user-applied force exerted on the handle assembly into the jaw members.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/843,297, filed on Sep. 2, 2015, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 62/050,496,filed on Sep. 15, 2014, the entire disclosures of each of which areincorporated by reference herein.

BACKGROUND Technical Field

The present disclosure relates to surgical instruments. Moreparticularly, the present disclosure relates to vessel-sealing devicesincluding force-balance interfaces and electrosurgical systems includingthe same.

Background of Related Art

Electrosurgical instruments have become widely used by surgeons.Electrosurgery involves the application of electrical energy and/orelectromagnetic energy to cut, dissect, ablate, coagulate, cauterize,seal or otherwise treat biological tissue during a surgical procedure.Electrosurgery is typically performed using an electrosurgical generatoroperable to output energy and a handpiece including a surgicalinstrument (e.g., end effector) adapted to transmit energy to a tissuesite during electrosurgical procedures. Electrosurgery can be performedusing either a monopolar or a bipolar instrument.

The basic purpose of both monopolar and bipolar electrosurgery is toproduce heat to achieve the desired tissue/clinical effect. In monopolarelectrosurgery, devices use an instrument with a single, activeelectrode to deliver energy from an electrosurgical generator to tissue.In monopolar electrosurgery, a patient return electrode, also called agrounding pad, bovie pad, neutral electrode or patient plate, isattached externally to the patient (e.g., a plate positioned on thepatient's thigh or back) as the means to complete the electrical circuitbetween the electrosurgical generator and the patient. When theelectrosurgical energy is applied, the energy travels from the activeelectrode, to the surgical site, through the patient and to the returnelectrode. In bipolar electrosurgery, both the active electrode andreturn electrode functions are performed at the site of surgery. Bipolarelectrosurgical devices include two electrodes of opposite polarity thatare located in proximity to one another for the application of currentbetween their surfaces. Bipolar electrosurgical current travels from oneelectrode, through the intervening tissue to the other electrode tocomplete the electrical circuit, thereby eliminating the need for aremotely-located current return. Bipolar instruments generally includeend-effectors, such as grippers, cutters, forceps, dissectors and thelike.

Forceps utilize mechanical action to constrict, grasp, dissect and/orclamp tissue. By utilizing an electrosurgical forceps, a surgeon canutilize both mechanical clamping action and electrosurgical energy toeffect hemostasis by heating the tissue and blood vessels to cauterize,coagulate/desiccate, seal and/or divide tissue. Bipolar electrosurgicalforceps utilize two generally opposing electrodes that are operablyassociated with the inner opposing surfaces of an end effector and thatare both electrically coupled to an electrosurgical generator. Inbipolar forceps, the end-effector assembly generally includes opposingjaw assemblies pivotably mounted with respect to one another. In bipolarconfiguration, only the tissue grasped between the jaw assemblies isincluded in the electrical circuit.

By utilizing an electrosurgical forceps, a surgeon can cauterize,coagulate/desiccate and/or seal tissue and/or simply reduce or slowbleeding by controlling the intensity, frequency and duration of theelectrosurgical energy applied through the jaw assemblies to the tissue.Tissue or vessel sealing is a process of liquefying the collagen,elastin and ground substances in the tissue so that they reform into afused mass with significantly-reduced demarcation between the opposingtissue structures. Cauterization involves the use of heat to destroytissue and coagulation is a process of desiccating tissue wherein thetissue cells are ruptured and dried.

Since tissue sealing procedures involve more than simply cauterizingtissue, to create an effective seal the procedures involve precisecontrol of a variety of factors. During the sealing process, mechanicalfactors such as the pressure applied between opposing jaw assemblies andthe gap distance between the electrically-conductive tissue-contactingsurfaces (electrodes) of the jaw assemblies play a role in determiningthe resulting thickness of the sealed tissue and effectiveness of theseal.

A variety of types of end-effector assemblies have been employed forvarious types of electrosurgery using a variety of types of monopolarand bipolar electrosurgical instruments. Electrosurgical instruments mayinclude a movable handle and a drive assembly adapted to impart movementto one or more components of the end-effector assemblies. The movablehandle may have a form that fits limited hand sizes.

SUMMARY

The handles on surgical instruments, such as vessel-sealing devices,often are challenging to design in a manner that enables the surgeon toeasily apply the required force to optimize the sealing function incoordination with the bipolar electrical current. The handles may limitmovement as they may interfere with other instruments or the table orthe abdomen of the patient. Further complicating the user interface arethe preloaded springs which are often used to fix the tissue compressionto a predetermined pressure when the handles are fully closed. This mayalso result in greater handle movement than is needed to fully operatethe jaw members.

According to an aspect of the present disclosure, a surgical instrumentis provided that includes a handle assembly, a shaft, an end-effectorassembly including opposing jaw members, and a powered force applicator.Jaw movement and jaw closure force are applied by the powered forceapplicator. The handle assembly is configured to transmit a signalindicative of a force exerted on the handle assembly, e.g., based on asmall amount of actual movement of the handle assembly, which istransmitted to the powered force applicator. Force applied by thepowered force applicator via the shaft to the jaw members is a multipleof the force exerted on the handle assembly.

According to another aspect of the present disclosure, while energy isapplied through the jaw members to tissue, the force applied to thetissue is controlled only by the powered force applicator in order toassure a correct relationship between the intensity, frequency andduration of the energy applied through the jaw members to the tissue,and tissue pressure necessary to effect a proper and effective tissueseal.

According to another aspect of the present disclosure, a surgicalinstrument is provided that includes a housing having a shaft affixedthereto, a reciprocatable drive rod slideably disposed at leastpartially within the shaft, and a force applicator coupled to the driverod. The shaft includes first and second jaw members attached to adistal end thereof, at least one of which movable relative to the otherfrom a first position wherein the jaw members are disposed in spacedrelation relative to one another to at least a second position closer toone another wherein the jaw members cooperate to grasp tissuetherebetween. The force applicator and the drive rod mechanicallycommunicate to impart movement to one or both of the jaw members. Thesurgical instrument includes a handle assembly and a force-balanceinterface. The force-balance interface is configured to translate amultiple of the user-applied force exerted on the handle assembly intothe jaw members.

According to another aspect of the present disclosure, anelectrosurgical system is provided. The electrosurgical system includesan electrosurgical energy source and an electrosurgical instrumentoperably coupled to the electrosurgical energy source. Theelectrosurgical instrument includes a housing having a shaft affixedthereto, a reciprocatable drive rod slideably disposed at leastpartially within the shaft, and a force applicator coupled to the driverod. The shaft includes an end-effector assembly wherein the forceapplicator and the drive rod mechanically communicate to impart movementto the end-effector assembly. The electrosurgical instrument includes ahandle assembly and a first force-balance interface. The handle assemblyis disposed in association with the housing. The first force-balanceinterface configured to translate a multiple of the user-applied forceexerted on the handle assembly into the end-effector assembly.

In any of the aspects, the force applicator may include electrical,pneumatic, and/or hydraulic components configured to exert a force onthe drive rod which results in movement and/or increasing pressurebetween the jaw members.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently-disclosed force-balance interfacesfor use in surgical instruments, such as vessel-sealing devices, e.g.,bipolar forceps, and electrosurgical systems including the same willbecome apparent to those of ordinary skill in the art when descriptionsof various embodiments thereof are read with reference to theaccompanying drawings, of which:

FIG. 1 is a perspective view, partially shown in phantom lines, of abipolar forceps shown in an open configuration and including a handleassembly and a force-balance interface in accordance with an embodimentof the present disclosure;

FIG. 2 is side view of the bipolar forceps of FIG. 1 with the internalworking components of the forceps exposed in accordance with anembodiment of the present disclosure;

FIG. 3 is side view of the bipolar forceps of FIG. 2 with the internalworking components of the forceps exposed in accordance with anembodiment of the present disclosure;

FIG. 4 is a perspective view, partially shown in phantom lines, of abipolar forceps shown in a closed configuration and including a handleassembly and a force-balance interface in accordance with an embodimentof the present disclosure;

FIG. 5 is a side, partial internal view of the end-effector assembly ofFIG. 1 shown with a schematically-illustrated force applicator inaccordance with an embodiment of the present disclosure;

FIG. 6 is a side, partial internal view of the end-effector assembly ofFIG. 1 shown with a schematically-illustrated pneumatic force applicatorin accordance with another embodiment of the present disclosure;

FIG. 7 is an enlarged, rear perspective view of the end-effectorassembly of FIG. 1 shown grasping tissue;

FIG. 8 is an enlarged, cross-sectional view of a tissue seal;

FIG. 9 is a schematic diagram of a force-balance circuit in accordancewith the present disclosure; and

FIG. 10 is a diagrammatic representation of a force-balance interface inaccordance with the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of a force-balance interface for use insurgical instruments, such as vessel-sealing devices, e.g., bipolarforceps, and electrosurgical systems including the same of the presentdisclosure are described with reference to the accompanying drawings.Like reference numerals may refer to similar or identical elementsthroughout the description of the figures. As shown in the drawings andas used in this description, and as is traditional when referring torelative positioning on an object, the term “proximal” refers to thatportion of the apparatus, or component thereof, closer to the user andthe term “distal” refers to that portion of the apparatus, or componentthereof, farther from the user.

This description may use the phrases “in an embodiment,” “inembodiments,” “in some embodiments,” or “in other embodiments,” whichmay each refer to one or more of the same or different embodiments inaccordance with the present disclosure.

Various embodiments of the present disclosure provide surgicalinstruments including a force-balance interface. Various embodiments ofthe present disclosure provide surgical instruments suitable forsealing, cauterizing, coagulating, desiccating, cutting, and/ordissecting vessels and vascular tissue. Various embodiments of thepresent disclosure provide an bipolar forceps including a force-balanceinterface and an end-effector assembly including two jaw membersdisposed in opposing relation relative to one another. Embodiments ofthe presently-disclosed bipolar forceps including a force-balanceinterface may be suitable for utilization in endoscopic surgicalprocedures, and/or suitable for utilization in open surgicalapplications.

Embodiments of the presently-disclosed surgical instruments including aforce-balance interface may be implemented using a variety of types ofenergy, e.g., electrosurgical energy at radio frequencies (RF) or atother frequencies, ultrasonic, optical, and/or thermal energy.Embodiments of the presently-disclosed surgical instruments may beconnected through a suitable bipolar cable to a generator and/or othersuitable power source. Although the following description describes theuse of a bipolar forceps, the teachings of the present disclosure mayalso apply to a variety of surgical devices with an end-effectorassembly and including a handle assembly and other components whichmutually cooperate to impart movement to one or more components of theend-effector assembly.

In FIGS. 1 through 3 , an embodiment of a bipolar forceps 400 includinga force-balance interface is shown for use with various surgicalprocedures. Forceps 400 generally includes a housing 420, a handleassembly 430, a rotating assembly 480, a trigger assembly 470, and anend-effector assembly 401. End-effector assembly 401 generally includestwo jaw members 410 and 420 disposed in opposing relation relative toone another. Forceps 400 may include additional, fewer, or differentcomponents than shown in FIGS. 1 through 3 , depending upon a particularpurpose or to achieve a desired result.

Forceps 400 includes a shaft 412 having a distal end 416 configured tomechanically engage the end-effector assembly 401 and a proximal end 414configured to mechanically engage the housing 420. Rotatable assembly480 is operatively associated with the housing 420 and is rotatableapproximately 180 degrees about a longitudinal axis “A-A” defined by theshaft 412. As shown in FIG. 1 , the end-effector assembly 401 isrotatable about the longitudinal axis “A-A” through rotation, eithermanually or otherwise, of the rotatable assembly 480. One or morecomponents of the bipolar forceps 400, e.g., the housing 420, the handleassembly 430, the rotatable assembly 480, the trigger assembly 470,and/or the end-effector assembly 401, may be adapted to mutuallycooperate to grasp, seal and/or divide tissue, e.g., tubular vessels andvascular tissue (e.g., 720 shown in FIGS. 7 and 8 ).

End-effector assembly 401 may be configured as a unilateral assembly,i.e., the end-effector assembly 401 may include a stationary or fixedjaw member, e.g., 420, mounted in fixed relation to the shaft 412, and amoveable jaw member, e.g., 410, mounted about a pivot pin 403 coupled tothe fixed jaw member. Alternatively, the forceps 410 may include abilateral assembly, i.e., both jaw members 410 and 420 are moveablerelative to one another. Jaw members 410 and 420 may be curved atvarious angles to facilitate manipulation of tissue and/or to provideenhanced line-of-sight for accessing targeted tissues.

In some embodiments, as shown in FIG. 1 , forceps 400 includes anelectrosurgical cable 415. Electrosurgical cable 415 may be formed froma suitable flexible, semi-rigid or rigid cable, and may connect directlyto an electrosurgical power generating source 428. Electrosurgical powergenerating source 428 may be any generator suitable for use withelectrosurgical devices, and may be configured to provide variousfrequencies of electromagnetic energy. Examples of electrosurgicalgenerators that may be suitable for use as a source of electrosurgicalenergy include generators sold by Covidien Surgical Solutions ofBoulder, Colo., e.g., Ligasure™ generator, FORCE EZ™ electrosurgicalgenerator, FORCE FX™ electrosurgical generator, and FORCE TRIAD™electrosurgical generator FORCE 1C™ generator, FORCE 2™ generator,SurgiStat™ II, or other generators which may perform different orenhanced functions. Forceps 400 may alternatively be configured as abattery-powered wireless instrument.

Handle assembly 430 includes a fixed handle 425 and a handle 440 thathas a relatively fixed position. Handle 440 is preloaded with a positiveforce against a sensor 492 by a spring (e.g., spring 493 a shown in FIG.2 , or spring 493 b shown in FIG. 3 ). As seen in FIGS. 2 and 3 , handle440 is selectively movable to increase or decrease force applied to thesensor 492 above or below the preload. Powered force applicator 450extends drive rod 454 in the direction “A” until the force of 450against the jaw members 410 and 420 reaches a balance force. The balanceforce is equal and oppositely applied through the powered forceapplicator 450 against the handle 440 and results in reaction to bringthe sensor 492 back to its preloaded condition. End-effector assembly401 is configured to allow the jaw members 410 and 420 to move freelyuntil, either, tissue is compressed between the inner surfaces (e.g.,electrically-conductive sealing plates) of the jaw members 410 and 420,or tissue is extended on the outer surfaces of the jaw members 410 and420. The resistance of the tissue is force transmitted back through tothe sensor 454. The lever advantage is through the relative differencesin the distance between the powered force applicator 450 and the hinge445, the force sensor 492, and the user's grip location on the handle440.

Forceps 400 includes a force-balance interface adapted to translateuser-applied force exerted on the handle assembly 430 into the jawmembers 410 and 420. In some embodiments, as shown in FIG. 4 , theforce-balance interface includes a first force-balance interface 490 a(also referred to herein as a “force-balance handle interface 490 a”)and a second force-balance interface 490 b (also referred to herein as a“force-balance jaw interface 490 b”). Force-balance handle interface 490a includes one or more force sensors (e.g., two force sensors 491 and492) disposed in association with the handle assembly 430, or componentthereof (e.g., movable handle 440). Force sensors 491 and 492 mayinclude any suitable device configured to generate an electrical signalindicative of the user-applied force exerted on the handle assembly 30.Force-balance jaw interface 490 b includes one or more force sensors(e.g., force sensor 497) disposed in association with the end-effectorassembly 101, or component thereof (e.g., jaw member 420).

In some embodiments, a piezoelectric or electromechanical force sensormay be utilized for the force sensor 491, the force sensor 492, and/orthe force sensor 497. In some embodiments, the force sensor 491, 492and/or 497 may be composed of a flex circuit. An example of a flexiblecircuit type sensor that may be suitable for use as the force sensor491, 492 and/or 497 is commercially available under the trademarkFlexiForce® offered by Tekscan of Boston, Mass. A variety of otherforce-sensing technologies such as load cells, piezoresistive, andcapacitive sensors also may be utilized for the force sensor 491, 492and/or 497.

Force sensor 491, 492 and/or 497 may be communicatively coupled to acontroller (e.g., controller 24 shown in FIGS. 5 and 6 ). In someembodiments, the controller may be configured to control one or moreoperating parameters of the end-effector assembly 401 responsive, atleast in part, to one or more electrical signals received from the forcesensor 491, the force sensor 492, and/or the force sensor 497. In someembodiments, the controller may be communicatively-coupled to a forceapplicator and configured to control the rate of closure of the jawmembers 410 ad 420, e.g., during activation, and/or control thecompressive force (e.g., “F” shown in FIG. 7 ) exerted by the jawmembers 410 and 420 and/or other operating parameters of theend-effector assembly 401 responsive, at least in part, to one or moreelectrical signals received from the force sensor 491, the force sensor492, and/or the force sensor 497.

In FIG. 4 , an embodiment of a bipolar forceps 700 is shown for use withvarious surgical procedures. Bipolar forceps 700 includes a handleassembly 730, which includes a first handle 725 and a second handle 740.Bipolar forceps 700 includes the force-balance interface of the bipolarforceps 400 (FIGS. 1 through 3 ), wherein the two force sensors 491 and492 are disposed in association with the second handle 740. Bipolarforceps 700 is similar to the bipolar forceps 400 shown in FIGS. 1through 3 , except for the configuration of the handle assembly 730, andfurther description with respect to the same elements is omitted hereinfor brevity.

In some embodiments, the first handle 725 is integrally associated withthe housing 420. Second handle 740 or portion thereof (e.g., gripportion) is formed of a resilient material. Second handle 740 mayinclude one or more ergonomic enhancing elements to facilitate handling,e.g., scallops, protuberances, elastomeric material, etc. Responsive touser-applied force “F” exerted on the second handle 740, the forcesensor 491 and/or the force sensor 492 generates one or more electricalsignals indicative of the user-applied force “F”. Based, at least inpart, on one or more signals generated by the force sensor 491 and/orthe force sensor 492, the controller (e.g., controller 24 shown in FIGS.5 and 6 ) and/or other circuitry (not shown) may adjust one or moreoperating parameters associated with the end-effector assembly 401and/or one or more operating parameters associated with theelectrosurgical energy source 428.

FIG. 5 shows the shaft 12 and the end-effector assembly 401 of FIG. 1operably associated with a knife 190, a drive rod 454, and a forceapplicator 800 in accordance with the present disclosure. Forceapplicator 800 generally includes an electric motor 802 powered by apower source 804, e.g., a stand-alone low-voltage DC source (e.g.,battery) or an integrated low-voltage power source as part of theelectrosurgical energy source (e.g., 428 shown in FIG. 1 ). Although theend-effector assembly 401 is shown, it is to be understood that otherend-effector assembly configurations may be used, which may includeadditional, fewer, or different components than shown in FIG. 8 .

Drive rod 454 includes a threaded portion 808 disposed in mechanicalcommunication with the motor 802. In some embodiments, as shown in FIG.8 , the motor 802 includes a gear box 806 that is mechanically coupledto the threaded portion 808 so that when the motor 802 is activated, thegears of the gear box 806 rotate and thereby longitudinally move thedrive rod 454. Pulling the drive rod 454 proximally and moving the jawmembers 410 and 420 apart, or pushing the drive rod 454 distally andmoving the jaw members 410 and 420 together, is accomplished by varyingthe direction of rotation of the motor 802. The rate of closure of thejaw members 410 and 420 may be controlled by varying the gears withinthe gear box 806 and/or adjusting the power supplied to the motor 802,which, in turn, adjusts the rate of rotation and torque exerted on thedrive rod 454.

Force applicator 800 is communicatively-coupled to a controller 24.Controller 24 may include any type of computing device, computationalcircuit, or any type of processor or processing circuit capable ofexecuting a series of instructions that are stored in a memory (notshown) associated with the controller 24, where memory may be any deviceor medium that can store code and/or data. Functions of the controller24 can be performed in hardware and/or software, as desired. In someembodiments, the controller 24 may be disposed in association with thehousing, the handle assembly, or other component of the device (e.g.,forceps 400 shown in FIG. 1 , and forceps 700 shown in FIG. 4 ) ordisposed in association with the electrosurgical energy source (e.g.,428 shown in FIG. 1 ).

Controller 24 may include logic, circuitry and/or code adapted tocontrol the motor 802 responsive to one or more electrical signalsreceived from one or more force sensors (e.g., force sensors 491, 492and 497 shown in FIGS. 1 and 3 ). In some embodiments, the controller 24may be configured to receive user-inputs from one or more user-inputdevices, including without limitation, a joystick, trackball,touchscreen, and/or other user-input device. Controller 24 may beconfigured to automatically adjust the operating parameters of the motor802 based on user input and/or electrical signals received from one ormore force sensors associated with any one of the above-describedforce-balance interfaces.

In some embodiments, the controller 24 may additionally, oralternatively, be configured to electrically, mechanically orelectro-mechanically adjust the distance the stop members (not shown)project by retracting or extending the stop members from the sealingplate. As a result, the gap distance “G” is adjusted by changing thedistance that the stop members project from the sealing plate.

In some embodiments, the presently-disclosed forceps (e.g., forceps 400shown in FIG. 1 , and forceps 700 shown in FIG. 4 ) may be configured toshift to an absolute force sensor 792 a or 792 b (FIG. 5 ), e.g.,located separately from the force sensors of the force-balanceinterface, and drive to a predetermined force (e.g., “F” shown in FIG. 7) and/or pressure (e.g., between about 3 kg/cm² to about 16 kg/cm²)applied between the opposing jaw members, e.g., before and duringactivation of energy, wherein the motor 802 is prevented from reversingwhen the user initiates a seal cycle.

FIG. 6 shows the shaft 12 and the end-effector assembly 401 of FIG. 1operably associated with a knife 190, a drive rod 454, and a forceapplicator 900 in accordance with the present disclosure. Forceapplicator 900 includes a linear actuator 902 powered by the powersource 804. The linear actuator 902 includes a housing cylinder 910 anda shaft 908.

As seen in FIG. 9 , the shaft 908 is mechanically coupled to the driverod 454 at an interface 904. In some embodiments, the housing cylinder910 of the linear actuator 902 is mechanically coupled to the interiorwall of the housing of the forceps (e.g., housing 420 shown in FIGS. 1and 4 ) at an interface 906. Linear actuator 902 moves the drive rod 454in a longitudinal direction proximally or distally by expanding orcontracting, respectively, between the interfaces 904 and 906. Linearactuator 902 may include an electric motor or a pneumatic or hydrauliccylinder that extends or retracts the shaft 908. Those skilled in theart will readily appreciate that if the linear actuator 902 ispneumatic, the shaft 908 may be part of the pneumatic cylinder. Powersource 804 is connected to the linear actuator 902 and provideselectrical power thereto. In some embodiments, the controller 24controls the operating parameters of the linear actuator 902, either,directly, or by controlling the power source 804, e.g., based on userinput and/or electrical signals received from one or more force sensorsassociated with any one of the above-described force-balance interfaces.

Turning now to FIG. 7 , the end-effector assembly 401 of an embodimentof the above-described forceps with a force-balance interface is shownduring a sealing procedure. In FIG. 7 , the end-effector assembly 401 isshown grasping tissue 720. In some embodiments, the end-effectorassembly 401 may include a gap distance “G” between opposing sealingsurfaces during sealing, e.g., in the range from about 0.001 inches toabout 0.006 inches. In some embodiments, the end-effector assembly 401includes a gap distance “G” between opposing sealing surfaces duringsealing that ranges from about 0.002 to about 0.003 inches.

As energy is selectively transferred to the end-effector assembly 401and applied to the opposing jaw members 410 and 420 and through thetissue 720 held therebetween, a tissue seal 750 forms isolating twotissue halves 720 a and 720 b (see FIG. 8 ). In some embodiments, aknife assembly (e.g., 190 shown in FIG. 5 ), e.g., activated via thetrigger assembly 470 (FIG. 1 ), progressively and selectively dividesthe tissue 720 along a tissue plane in a precise manner to divide thetissue 720 into two sealed halves (not shown). Once the tissue 720 isdivided into tissue halves, the jaw members 410 and 420 may be opened byre-initiation or re-grasping of the handle 440.

In FIG. 9 , a force-balance circuit 900 is shown in accordance with thepresent disclosure. Force-balance circuit 900 generally includes a forceapplicator 910, e.g., a motor, and an H-bridge 920. An op amp circuit isused as a conditioner for the resistive-element force sensor 990. Thevoltage from the force sensor 990 is biased by a resistor and twopotentiometers R2 and R3 provide reference voltages to two comparators,which may be used to advance the motor 910 drive forward or in reverse.The two comparators provide output to the H-bridge 920. The firstcomparator provides an output signal when voltage from force sensor 990indicates increasing forward motion of the force applicator motor 910and the second comparator provides an output signal when the voltageindicates reversing the force applicator motor 910 to reduce forcedelivered through the shaft to the jaw members 410 and 420. The tworeference voltages for the two comparator may be offset from each othersuch that only one comparator outputs to the H-bridge 920 at a time.Generally this provides a dead zone when the force of the handle 440 andforce applicator are matched and the motor 910 is off. One canappreciate the simplicity and low cost of the circuit and its adequacyfor control and that an equivalent variable output circuit could beconstructed to perform similar function at greater complexity.

FIG. 11 is a diagrammatic representation of a force-balance interface inaccordance with the present disclosure. Increasing the input force(illustratively depicted by the arrowed line in FIG. 11 ) compresses thetwo springs, thereby moving the sensor plate to the “forward drive”position. The motor extends the linear actuator until the springs areoppositely compressed, thereby returning the sensor plate to a neutralposition. Decreasing the input force has the opposite effect, e.g.,causing the sensor plate to move to the “reverse drive” position.

The above-described bipolar forceps embodiments include a force-balanceinterface and may be suitable for use in a variety of procedures andoperations. The above-described end-effector embodiments may utilizeboth mechanical clamping action and electrical energy to effecthemostasis by heating tissue and blood vessels to coagulate, cauterize,cut and/or seal tissue. The jaw members may be either unilateral orbilateral. The above-described bipolar forceps embodiments that includea force-balance interface may be suitable for utilization withendoscopic surgical procedures and/or hand-assisted, endoscopic andlaparoscopic surgical procedures. The above-described bipolar forcepsembodiments may be suitable for utilization in open surgicalapplications.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

What is claimed is:
 1. A surgical instrument, comprising: a housing; ashaft extending distally from the housing; an end effector disposedadjacent a distal portion of the shaft and including a first jaw memberand a second jaw member, at least one of the first jaw member or thesecond jaw member movable relative to the other jaw member; a handleassembly including a movable handle, wherein actuation of the movablehandle causes the at least one of the first jaw member or the second jawmember to move relative to the other jaw member; and a force-balanceinterface configured to translate a multiple of a user-applied forceexerted on the handle assembly into at least one of the first jaw memberor the second jaw member, the force-balance interface including at leastone force sensor configured to be contacted by the movable handle duringa range of motion thereof, wherein the at least one jaw member movesrelative to the other jaw member prior to the movable handle contactingthe at least one force sensor.
 2. The surgical instrument according toclaim 1, wherein the handle assembly includes the movable handle and afixed handle.
 3. The surgical instrument according to claim 2, whereinthe movable handle is pivotable relative to the fixed handle.
 4. Thesurgical instrument according to claim 1, wherein the movable handle ismovable between a first position where the movable handle is free fromcontact with the at least one force sensor, and a second position wherethe movable handle is in contact with the at least one force sensor. 5.The surgical instrument according to claim 1, further including a driverod slidably disposed at least partially within the shaft.
 6. Thesurgical instrument according to claim 5, further including a forceapplicator coupled to the drive rod, wherein the force applicator andthe drive rod mechanically communicate to impart movement to the atleast one jaw member.
 7. The surgical instrument according to claim 6,further including a controller communicatively-coupled to the at leastone force sensor and communicatively-coupled to the force applicator. 8.The surgical instrument according to claim 7, wherein the forceapplicator includes an electric motor.
 9. The surgical instrumentaccording to claim 7, wherein the force applicator includes a linearactuator.
 10. The surgical instrument according to claim 9, wherein thecontroller is configured to control at least one operating parameter ofthe linear actuator based on at least one signal received from the atleast one force sensor.
 11. The surgical instrument according to claim1, wherein the at least one force sensor is configured to transmit asignal indicative of the user-applied force exerted on the handleassembly.
 12. The surgical instrument according to claim 11, furtherincluding a controller communicatively-coupled to the at least one forcesensor.
 13. The surgical instrument according to claim 1, wherein themovable handle is preloaded with a positive force against the at leastone force sensor by a spring.
 14. A surgical instrument, comprising: ahousing; a shaft extending distally from the housing; an end effectordisposed adjacent a distal portion of the shaft and including a firstjaw member and a second jaw member, at least one of the first jaw memberor the second jaw member movable relative to the other jaw member; anactuator, wherein actuation of the actuator causes the at least one jawmember to move relative to the other jaw member; and at least one forcesensor configured to be engaged by the actuator, wherein the at leastone jaw member moves relative to the other jaw member prior to theactuator engaging the at least one force sensor.
 15. The surgicalinstrument according to claim 14, wherein the actuator is movablebetween a first position where the actuator is free from contact withthe at least one force sensor, and a second position where the actuatoris in contact with the at least one force sensor.
 16. The surgicalinstrument according to claim 14, further including a drive rod slidablydisposed at least partially within the shaft.
 17. The surgicalinstrument according to claim 16, further including a force applicatorcoupled to the drive rod, wherein the force applicator and the drive rodmechanically communicate to impart movement to the at least one jawmember.
 18. The surgical instrument according to claim 14, wherein theactuator is preloaded with a positive force against the at least oneforce sensor by a spring.
 19. The surgical instrument according to claim14, wherein the at least one sensor is included on a first force-balanceinterface, the first force-balance interface configured to translate amultiple of a user-applied force exerted on the actuator into at leastone of the first jaw member or the second jaw member.